Horizontal directional drilling, commonly referred to as HDD, is a process used in applications such as installing utilities underground. Generally the first step in the HDD process includes boring a pilot hole. In this step a bore hole is created that extends underground—generally horizontally or parallel to the surface of the earth—starting at a launch point and ending at a termination point.
The bore hole is created by a boring machine that rotates and pushes a drill string through the ground. A drill bit is attached to the leading end of the drill string. The drill string is formed by connecting individual drill rods together end-to-end. The connection between the rods is made up, and subsequently broken in a later step, by the boring machine. A typical boring machine includes a gearbox that connects to the drill string, a drill rod storage magazine, and a rod loading mechanism. The rod loading mechanism moves the individual drill rods from the storage magazine into alignment with the drill string and the gearbox where the individual drill rod is connected to and made a part of the drill string.
Rod loading mechanisms typically include a rod transfer mechanism that moves the rod from the storage magazine and positions it with one end in alignment with the drill string and the other end in alignment with the gearbox. The drill rods are typically long, and are stored with their longitudinal axes parallel to one another. There are generally several separated, parallel columns in the storage magazine for storing the drill rods, with each subsequent column further from the drill string. Accordingly, the rod loading magazine is generally heavy and bulky.
The drill rod storage magazine may be interchangeable with other magazines. In this type of arrangement, once all of the drill rods stored in a first magazine are used, the empty first magazine can be replaced with a full second magazine. In this manner, a longer drill string may be formed. However, because of the weight of the magazine, special equipment such as a back-hoe, front end loader or other hydraulic equipment capable of lifting the magazine must generally be employed to remove the empty first magazine and replace it with a full second magazine (e.g., the second magazine has an additional supply of drill pipe located therein).
A drawback exists, however, with these systems since there are occasions when only one (or a relatively few) additional drill rods are required for the drill string. Also, there may be instances when the necessary power equipment is not available to lift and replace the magazine. Still further, there may be instances when specific drill pipe is desired to be inserted into the drill string. Therefore, there is a need in the art for a method and apparatus for selectively loading drill rod into a magazine. The present invention overcomes the shortcomings of the prior art and addresses these needs in the art.